Dye compounds as represented in the below formula (hereinafter, sometimes referred to as “benzodifuranone-based dye compound”), having two 5-membered lactone rings fused to central cyclohexa-1,4-diene nucleus, have good fastness properties such as washing fastness and sublimation fastness, whereby they are generally employed in dyeing of high functionality fiber materials such as leisure- and sports-ware. However, many prior art benzodifuranone-based compounds fail to provide satisfactory properties in dyeing of some synthetic fiber materials, especially micro fibers. In other words, these benzodifuranone-based compounds exhibit a low dyeability and fastness to micro fibers.

Examples of these benzodifuranone-based compounds are disclosed in U.S. Pat. No. 5,286,881, Korean Patent No. 138,255, etc., and α-hydroxy benzeneacetic acid as represented in the below formula acid is used as a precursor indispensable for synthesis of the benzodifuranone-based compounds.

In connection with the preparation process of this α-hydroxy benzeneacetic acid (or nitrile compound thereof), there are U.S. Pat. No. 4,368,334, U.S. Pat. No. 6,359,172, British Patent No. 1,576,331, Japanese Laid-open Patent No. S56-68641, etc. In these prior art processes, α-hydroxy benzeneacetic acid is produced using phenol and glyoxylic acid.
As a process for introduction of short alkoxy group to the above α-hydroxy benzeneacetic acid, British Laid-open Patent No. 2,101,998A shows a technology of condensing the mandelic acid with propyl bromide with the aid of sodium hydroxide in water. However, in accordance with this process, the condensation reaction must be run at low temperature for a long time due to the low boiling point of propyl bromide, and also propyl bromide must be continuously added to the reaction procedure so as to replace the amount of propyl bromide lost, and the synthesized compound is produced in the form of cake, which makes a high purity and yield difficult to achieve. If alkoxy bromide with a high boiling point is employed in the above reaction, the reaction temperature must be adjusted to high temperature to maintain an acceptable reaction rate, resulting in the decomposition of α-hydroxy benzeneacetic acid under the acid or alkali conditions.
In order to solve these problems, alternative approaches, as shown in Beilstein Handbuch der Organischen Chemie, enlarged edition Vol. System No. 1106/H410-411, Japanese Laid-open Patent No. S64-120058, and Korean Laid-open Patent No. 1995-18310, were developed whereby a substitute group is first introduced to hydroxyl benzaldehyde and the resulting compound is reacted with sodium hydrogensulfite and sodium cyanide, then hydrolyzed to produce a nitrile compound, which is briefly illustrated in the below reaction formula.
wherein R is as defined in Japanese Laid-open Patent No. S64-120058.
However, this process has drawbacks that the yield is very low at 50˜81% and an expensive apparatus is required to collect toxic hydrogen cyanide gas created by the reaction, and there is a possibility of water contamination resulting from toxic cyanide. Korean Laid-open Patent No. 1996-14044 suggests a process using cyanuric chloride in place of sodium hydrogen sulfite, as illustrated in the below reaction formula.
wherein R is as defined in Korean Laid-open Patent No. 1996-14044.
However, this process also has the same drawbacks as in the above process. Accordingly, there is a strong need for a novel process to effectively synthesize O-hydroxy benzeneacetic acid (including its derivatives) as an important precursor for synthesis of benzodifuranone-based compounds.